Method in a paper or pulp process to control the chemical state of the pulp and circulation water system

ABSTRACT

The invention relates to a method in a paper or pulp process to control the chemical state of the pulp and circulation water system. In the process one or more raw-material components (PROCESS WATER, TMP, PULP, REJECT) diluted in liquid, possible fillers, and one or more additives are mixed to form stock. In the method, the electrochemical state of at least one raw-material component (PROCESS WATER, TMP, PULP, REJECT) and/or the stock is regulated, without the regulation substantially affecting the pH values of the raw-material components (PROCESS WATER, TMP, PULP, REJECT) and/or of the stock.

[0001] The present invention relates to a method in a paper or pulpprocess to control the chemical state of the pulp and circulation watersystem, in which said process one or more raw-material componentsdiluted in liquid, possible fillers, and one or more additives are mixedto form stock.

[0002] At paper mills, various fibrous raw-material components arestored in storage towers. These are advantageously combined, to create awet-formable stock, i.e. a watery sludge of fibres and other rawmaterials for manufacturing paper.

[0003] The said raw-material components can be, for example, mechanicalspulps, for instance mechanical pulps from chips and groundwood pulps(SGW, RMP, TMP, etc.) or chemical pulps, such as cellulose. Nowadays, alarge amount of deinked waste paper fibre, i.e. so-called DIP pulp(DeInked Pulp) is also used, along with the reject pulp that arisesduring production, sometimes even in large quantities, and which is alsotaken as one of the raw-material components in stock preparation, toutilize it as efficiently as possible.

[0004] According to the state of the art, the control of the chemicalstate of the pulp and circulation water system, for example, the controlof phase changes, significantly affects the success of the papermakingprocess. The chemical state can be used to affect such things as therunnability properties of the machine, the paper quality, the dirtyingof the machine, the environmental load, and the operation of thewaste-water treatment plant of the paper or pulp mill. Disequilibrium inthe chemical state can lead to sedimentation, gas formation, anddiminished retention in the stock, for example.

[0005] According to the state of the art, several variables, such as pHlevel, salt content, and temperature are regulated in an attempt tocontrol the chemical state. This takes place, for example, by addingchemicals after the raw materials have been mixed.

[0006] If the raw-material components must be held in the storage towersfor a inconveniently long period, for example during a break inproduction, changes in their chemical state that are detrimental to theprocess may take place. Thus, for example, bacterial activity may resultin the formation of sulphur compounds, such as hydrogen sulphide, inchemical pulps. Similar problems also appear with DIP and reject pulps.

[0007] The changes in the chemical state of the raw-material componentscause uncontrollable reactions when the components are mixed in themixing tank of the paper machine. For example, sedimentations or gasesthat lead to porosity in the paper web can then arise. Such factorssubstantially weaken the runnability properties of the paper machine.

[0008] According to the state of the art, the pH value, i.e. the aciditylevel, presently appears to be an important variable, for example, incontrolling the chemical state of the raw material components of thepaper process, as changes take place in the charge level and solubilityof the wood material when the pH value changes. Good pH-value control isan essential variable in achieving even retention, i.e. the percentageof solids remaining in the web in the wire section compared to that inthe headbox feed. Further, the pH value affects not only the retentionsubstances, but also the action of other additives, the control of thephase changes, the runnability and dirtying of the machine, and thequality of the paper.

[0009] The pH value is controlled with the aid of lye or sulphuric acid,which can be dosed, for example, into the wire pit, either automaticallyor manually. Careful control movements are essential, as sudden changescan cause pH shocks or other disturbances. A sudden change in the pHvalue will cause the sedimentation of a dissolved or dispersedsubstance. Control of the pH value is slow, because the regulatingchemical must be allowed to enter the fibre and the pH measurement pointmust be located to provide the measurement result after a specificdelay.

[0010] On the other hand, controlling the pH value with the saidsubstances introduces additives, such as sodium and sulphur, which aredetrimental to the process, and which for their part will causeproblems, such as reduced retention, in the wire section.

[0011] The pH value is usually well controlled in the pulp andcirculation water system of a paper machine. However, attempts tocontrol phase changes in the paper process have generally taken placethrough sensitive control of the pH value, thus affecting, for instancethe general runnability of the machine, due to the varying charge level.

[0012] In the paper and pulp process, the state of the art is alsorepresented by the measurement of the charge levels of the liquids, forexample, through the definition of the zeta potential. However, as thisis a complicated way to carry out definition, it is very difficult andcannot be carried out with complete reliability directly from theproduction environment.

[0013] The present invention is intended to create an new type of methodin a paper or pulp process to control the chemical state of the pulp andcirculation water system. The paper process can also be held to includeboard and pulp manufacture. The characteristic features of the methodaccording to the invention are listed in the accompanying claim 1.

[0014] It has been observed that there may be quite natural significantdifferences in the electrochemical states of the raw-materialcomponents, without any particular disturbing factors. Thussedimentation or gas formation, for instance, can occur in the stock.The pilot-stage research has also shown that differences between theelectrochemical states of the raw-material components have a significanteffect on their mutual miscibility and the formation of bounds betweenthem. The method according to the invention is characterized by theregulation in the pulp and circulation water system of theelectrochemical state of at least one raw-material component and/or thestock. The regulation can be carried out on, for example, a raw-materialcomponent, on part of it, or on a mixture of two or more raw-materialcomponents, before the stock formation, or, for example, on the stock inthe short circulation, or before it is fed from the headbox to theweb-formation section.

[0015] In the method according to the invention no essential changes arecaused in the pH values of the raw-material components and/or of thestock. This has the effect of substantially reducing, among otherthings, the dosing cycle of additives, caused by the operating manneraccording to the state of the art.

[0016] In the method according to the invention, when a raw-materialcomponent and/or stock is in the reduction area, its electro-chemicalstate is regulated, for example, by equalizing it or increasing it inrelation to the other pulp components, according to one preferredembodiment by using a suitable oxidizing or reducing compound orsubstance, while the electro-chemical state of a raw-material componentin the oxidizing area is regulated by using a suitable reducing oroxidizing compound or substance.

[0017] According to a second preferred embodiment, the electrochemicalstate of a raw-material component or stock can be regulated byconnecting it to a selected potential level by means of an externalsource of alternating or direct current. Thus no additives are required.Further, the regulation by means of chemical can be used in conjunctionwith regulation using an external power source. In regulation carriedout using an external power source, the polarity can also be reversed.

[0018] According to a third preferred embodiment, in the methodaccording to the invention the electrochemical state of the process canbe regulated through the order of mixing the raw-material components.The order can be optimized to suit different running situations.

[0019] The method according to the invention substantially improves thecontrol of the chemical state, the paper quality, and the runnability ofthe machine in general, besides reducing the environmental load.Further, corrosion in the machine structures and in the pulp andcirculation water systems is significantly reduced and the formation ofgas diminishes, leading to a substantial improvement in the reliabilityof consistency measurements, among other things.

[0020] Further, the method according to the invention can also be usedto advantageously affect the retention of the wire section, the amountof fines, and possible bacteria growths in the liquid. This furtherreduces the need for chemicals. In addition, the method according to theinvention brings further advantages in improved paper strength andformation and in the control of the paper-web edges, which significantlyaffects the effective production capacity.

[0021] The other characteristic features of the method according to theinvention will be apparent from the accompanying Claims while otheradvantages to be gained are stated in the description section.

[0022] In the following, examples of embodiments relating to the methodaccording to the invention are examined with reference to theaccompanying drawings, in which

[0023]FIG. 1 shows a schematic example of one embodiment of the methodaccording to the invention,

[0024]FIG. 2a shows a schematic example of a second embodiment of themethod according to the invention, and

[0025]FIG. 2b shows a schematic example of a third embodiment of themethod according to the invention.

[0026]FIG. 1 shows a diagram of one preferred embodiment of the methodaccording to the invention, which depicts very roughly on a schematiclevel the pulp and circulation water system 10 of a paper machine 35.

[0027] In the pulp system, the storage towers 15, 14, 13 for theraw-material components (PULP, TMP, DIP) are shown. Raw materials arebrought to them along lines 15 a, 14 a, 13 a, for example, from a pulpmill, pulp pretreatment plants, such as disintegration (bale pulper) andgrinding, or other similar places (not shown). From the storage towers15, 14, the PULP and TMP pulps are lead along lines 15 b, 14 b throughpossible cleaners, defibrators, or other operational devices (not shown)to their dosing tanks 18, 19. The dispersed DIP pulp 13 can also be leadalong a line 13 b direct to the mixing tank 12. From the PULP and TMPdosing tanks 18, 19, the pulp is dosed to lines 18 b, 19 b, throughpossible beating stages (not shown), to the mixing tank 12.

[0028] On the paper machine 35, the headbox 27 and wire section 28 ofwhich are shown in FIG. 1, even large amounts of reject pulp can ariseat times, the necessary means for collecting and processing which, suchas conveyors and machine pulpers (not shown), are arranged in connectionwith the machine 35. Situations that create reject pulp arise, forexample, during web breaks, and particularly when problematicallyoperating production is being start up, when reject pulp is formed atthe production speed and over the production width of the machine 35.

[0029] Reject also arises during actual production running, as does, ona smaller scale, for example, edge strips cut on the machine 35 and edgeparts cut from reels during finishing, which annually represents aconsiderable amount of highly processed raw material, obtained fromlarge production inputs. Depending on the type of machine and the pointat which the reject pulp arises, the reject pulp may be coated oruncoated, i.e. so-called base reject.

[0030] Generally, separate processing is arranged for both types ofreject, including collection lines 20 a, 21 a for leading the rejectpulp, for example, from machine pulpers (not shown) to the storagetowers 20, 21 for coated and uncoated reject. The coated reject is ledon from the storage tower 20 along line 20 b to the reject tank 22 andon along line 22 b to the reject pulp dosing tank 24. The uncoatedreject is led along line 21 b, for example, through precipitation (notshown) to the reject tank 23, and from there along line 23 b to the samedosing tank 24 as the coated reject. From there, the reject pulp isdosed in a suitable ratio over line 24 b to the mixing tank 12.

[0031] In the mixing tank 12, the raw-material components are mixedtogether to form a so-called high consistency pulp, which is led alongline 25 a to the machine tank 25. From the machine tank 25, the highconsistency pulp is dosed over the line 25 b to the wire pit 30, inwhich it dilutes to form stock. The stock is transferred over line 34 tothe short circulation 26 of the paper machine 35, which incorporates,for instance, hydro-cyclone cleaning and deaeration devices, as well asfilters and pumps (not shown).

[0032] In the short circulation 26, the stock is diluted, sorted, andtransferred by a head feed pump (not shown) along line 27 a to theheadbox 27, which is used to spread the stock evenly to the subsequentwire section 28. In the wire section 28, the stock is wet-formed tocreate a paper web, when most of the water is removed from it.

[0033] In the headbox 27, a bypass circulation 31 is arranged, which isused to return excess stock that has been led there to the deaeration(not shown) of the short circulation 26. From the headbox 27 and thesubsequent wire section 28, devices 29 are used to collect the so-calledtail water, which contains both water and also material not retained inthe web (0-water).

[0034] The tail water is led by lines 27 b, 29 a to the wire pit 30,from which it is reused at various points in the pulp systems and theshort circulation 26. Besides the tail water, chemically purified waterand raw water are generally used in the processes, all of which togetherare referred to in the following as process water. An overflow 33 isarranged in the wire pit 30, the tail water from which is led by line 32a to the circulation water tank 32. Water is added from this, forexample, over line 32 b to the connecting line 25 a between the mixingtank 12 and the machine tank 25.

[0035] The addition of fillers and additives, diluted to suitableproportions (not shown), takes place, for example, in connection withthe wire pit 30.

[0036] It should be noted that the above description of the pulp andcirculation water systems of a paper machine 25 is given by way of arough example, so that it lacks, for example, inessential operatingdevices from the point of view of the invention, such as defibrators,pulpers, grinders, precipitators, sorters, and other intermediatestorage. In addition, implementations of the systems may also differfrom each other, due to the paper grades being manufactured and themachine concepts.

[0037] The method according to the invention can be advantageouslyapplied not only to the pulp and circulation water systems 10 shown inthe embodiment example, but also, for example, to a board machine andthe pulp manufacturing process.

[0038] In the method according to the invention, the electrochemicalstate of at least one raw-material component PROCESS WATER, TMP, PULP,REJECT, DIP, and/or the stock formed from them is controlled byregulation. According to one preferred embodiment, an attempt is made toequalize the electrochemical states of the raw-material components,before mixing them together. Thus, in addition to the aforementionedpulps, the process waters and generally the substances (for example,fillers and additives) mixed into the liquids in the processes describedcan also be regarded as raw-material components.

[0039] The electrochemical state of a raw-material component PROCESSWATER, TMP, PULP, REJECT, DIP can be expressed, for example, as thelevel of its electrical potential. In the method according to theinvention, the regulation of the electrochemical state of a raw-materialcomponent PROCESS WATER, TMP, PULP, REJECT, DIP involves according to afirst embodiment either raising or lowering the level of its potential,in such a way that the electrochemical states of the raw-materialcomponents fed into the mixing tank 12 are essentially more equalizedthan before their regulation, without substantially altering the pHvalue of the components, due to a rise or drop in the level of theirelectrochemical potential. According to a second preferred embodiment,the difference between the electrochemical states of the raw-materialcomponents can also be increased, to eliminate detrimental reactions andto increase advantageous reactions.

[0040] If the raw-material component PROCESS WATER, TMP, PULP, REJECT,DIP is in the oxidizing range before it is led to the mixing tank,according to a first embodiment a reducing agent (for example, sulphurdioxide, SO₂) is added to it, to reduce the value of the electricalpotential of the raw-material component to the chosen level, or else anoxidizing agent (for example, hydrogen peroxide H₂O₂) is added, to raisethe value of the electrical potential to a chosen level that isadvantageous to the mixing to be carried out with the other pulpcomponents.

[0041] Correspondingly, if the chemical state of the raw-materialcomponent is in the reducing range, the substance added to it is anoxidizing agent (for example, H₂O₂), which raises the electricalpotential to the chosen level. If it is desired to lower the potential,a reducing agent, for example SO₂, is added. In the method, it isessential for the said reducing or oxidizing agents to be added not toaffect the pH value of the raw-material components.

[0042]FIG. 1 shows an example, in which the bleaching of a mechanicalpulp TMP 14, carried out by using reducing dithionite (Na₂S₂O₄ ⁻²),significantly lowers the potential of the raw-material component,leading to unfavourable reactions in the process. According to apreferred embodiment, hydrogen peroxide (H₂O₂), for example, which has aknown reducing effect, can be added from the tank 17. The addition ismade through the line 17 b to the dosing tank 19, essentially before themixing tank 12, and thus before the formation of the stock. The additionof the hydrogen peroxide 17 raises the electrochemical state of the TMPpulp in question to a level at which it does not react when mixed withthe other raw-material components PULP, REJECT, thus preventingdisturbances that diminish the runnability of the machine 35, forexample.

[0043] Correspondingly, extremely detrimental hydrogen sulphide (H₂S),which strongly lowers the raw-material components into the reducingzone, can arise in chemical pulp PULP or especially in reject pulp. Thiscan be oxidized by adding, for example, hydrogen peroxide (H₂O₂) from atank 16 to the dosing tank 18 through a line 16 b, essentially beforethe mixing tank 12. Oxidizing can also be carried out simply by usingpure air. The electrochemical state of the pulp component PULP will thenrise to a favourable level, thus preventing detrimental reactions whenit is mixed with the other components TMP, REJECT, DIP.

[0044] It should be noted that the electrochemical states of theraw-material components may differ also very naturally, without anyspecific factor. The differences in level in the electrochemical statesof the raw-material components caused by the aforementioned dithioniteand hydrogen sulphide are only individual factors and in no way restrictthe scope of protection of the method according to the invention.

[0045] Thus, the electrical potentials of the raw-material componentsPROCESS WATER, TMP, PULP, REJECT, DIP are regulated before they are fedinto the mixing tank 12, or the electrochemical state of the stockformed from the raw-material components is regulated to an optimallevel, thus preventing detrimental chemical reactions, which cause, forexample, sedimentation or air bubbles in the stock. Differences in theelectrochemical states of the raw-material components or mixtures formedfrom them are permitted, in order to find the optimal level, depending,for example, on the running situation/manner, or on the other propertiesof the raw-material components.

[0046] An attempt is made to make any possible chemical sedimentationtake place, for example, only in the wire section 28 of the papermachine 35 and to create optimal retention, so that it will not createproblems, for example, in the mixing tank 12 or in the headbox 27.Instead of continuous regulation, regulation can also take place, tosuit the situation, as a shock effect in pulses, and not continuously.Using a shock effect, violent changes will be created in theelectrochemical state, so that a live bacterial strain will not thrive,as it cannot withstand violent changes in its living conditions.Regulation can take place also according to the process equipment, or byselecting an optimal liquid for each process.

[0047] Further, the electrochemical state of the stock formed from theraw-material components can be regulated after the formation of thestock, however, essentially before it is fed out of the headbox 27 ofthe paper machine 35 to the wire section 28.

[0048] In the method according to the invention, the minimum requirementfor determining the electrochemical state is only a single measurementof the electrical potential, in which the electrical potential of theliquid is measured in relation to a chosen reference electrode. If thepotential distribution is uneven, the number of measurement locationscan be increased to determine the average potential level. Examples ofthe said electrode are Fe, Pt, Rst, Cu, Au, Ag. In pilot-stage tests, ithas been observed that the raw-material components' potential levels canvary between, for example, −800 mV, PULP and +350 mV, REJECT.

[0049] According to a second preferred embodiment, the correction of anelectrochemical disequilibrium can be achieved in place of, or possiblyalong with the chemical additions described above, by means of anexternal alternating or direct current source 40.

[0050] In order to correct the chemical state with the aid of anexternal current source 40, one or several electrodes 40 connected to anexternal power supply are arranged, for example, in the dosing tanks 18,19, 22, 23, 24, or before or after them. This embodiment is mostadvantageous, for example, for implementing regulation that takes placein pulses and/or by reversing polarity.

[0051] Further, according to a third preferred embodiment, the order ofmixing the raw-material components PULP, TMP, DIP, REJECT can be used toequalize or increase their electrochemical states. For example, the tworaw-material components with the lowest potential levels are mixedfirst, and then these are mixed with the component with the next lowestlevel, and so on.

[0052] All of the types of regulation described above can be used singlyor in combinations. Further, in regulation it is possible to use, inaddition to or besides the above types, gas and/or salts, and/or amagnetic field, and in general all methods of regulation based onelectromagnetic radiation. In addition, lasers and ultrasound can beused in regulation.

[0053]FIGS. 2a and 2 b show further additional application examples ofpreferred embodiments of the method according to the invention. In both,the differences between the electrochemical states of the raw-materialcomponents, or of the divided parts of individual raw-materialcomponents are increased.

[0054] In the embodiment example shown in FIG. 2a, the electrochemicalstate of a raw-material component TMP used in the manufacture ofnewsprint is regulated in such a way as to reduce, or even in certaincases to omit entirely, the most cost-intensive amount of pulp requiredin the manufacture of the paper grade in question. The regulation of theelectrochemical state takes place by leading at least part of the TMPpulp to the manipulation M 40 of the electrochemical state, after whichboth the manipulated raw-material component TMPM and the unmanipulatedraw-material component TMP are mixed together. The difference inpotential created between the components creates advantageous reactions,thus allowing the amount of pulp to be reduced.

[0055]FIG. 2b shows a second embodiment example, in which the differencein the electrochemical state of the TMP pulp relative to the REJECT pulpis increased M 40 prior to them being combined. Correspondingly in thiscase, the increase in the difference between the electrochemical statesof the raw-material components TMP, REJECT allows the PULP component tobe reduced, and, in the best case, for it to be omitted.

[0056] In addition to the measurement of the electrical potential, theelectrochemical state of the raw-material components can be measuredusing other forms of electrochemical measurement, such as themeasurement of electrochemical noise, current measurement, measurementof the linear polarization resistance, and frequency measurement. In themeasurement of electrochemical noise (EN, Electrochemical Noise), thepotential or current noise, i.e. the fluctuation at a low frequency andamplitude, is measured between two identical electrodes. In themeasurement of linear polarization resistance (LPR) the speed of theoxidizing reactions taking place on the surface of a sensor is measured.The measurement reacts to such things as changes in the conductivity andtemperature of an electrolyte, i.e. diluting liquid, and theconcentrations of the oxidizing components.

[0057] In the method according to the invention, the chemical state canalso be controlled by means of electro-flocculation. In this embodiment,two or more electrodes of different models (for example, plates, rods,spheres), between which the direct/alternating current ratio and/or thepolarity is altered, can be arranged in parallel and/or in series.Further, the regulation parameters are affected by the electrodematerials used. The diluted raw-material component of the process water,or the stock is arranged to circulate through electrodes arranged inparallel in a bank of electrodes.

[0058] According to a first embodiment exploiting electro-flocculation,the elements in the raw-material components and/or in the stock can becharged electrically, so that the electrochemical conditions of theraw-material component and/or the stock can be regulated to beadvantageous to the process.

[0059] According to a second electro-flocculation embodiment, disturbingsubstances can be collected from the raw-material components and/or thestock onto electrodes, to prevent them from disturbing the process.

[0060] According to a third electro-flocculation embodiment, thematerials of the electrodes can be advantageously selected so thatadditives, which charge the fibres and/or particles in a raw-materialcomponent and/or the stock, thus advantageously affecting theelectrochemical state of the process, can be released from them.

[0061] The method according to the invention can also be used toadvantageously affect the retention in the wire section, becauseconditions favourable to retention can also be created by regulating theelectrochemical state of the stock, thus reducing the need to useretention agents. Further, the formation and strength of the paperimprove and the bacterial activity in the process water diminishes. Therunnability and level of cleanliness of the machine 35 also improve.

[0062] Yet another application of the method according to the inventionis the improvement of the properties of the edge parts of the paper web.According to the state of the art, the strength of the edge parts of thepaper web is weaker than that of the web on average. In part, this isdue to the fact that the temperature distribution of the dryingcylinders (not shown) of the dryer section of the paper machine 35 isuneven, so that the ends of the cylinders are hotter than the centralpart.

[0063] When applying the method according to the invention to theproblem, process water, the electrochemical state of which has beenregulated according to the method of the invention in an advantageouslydirection in terms of the desired effect, is added to the edge parts ofthe headbox 25 of the paper machine 35. This also improves theproperties of the edge parts of the paper web, thus increasing theeffective width of the web.

[0064] It should be understood that the above description and therelated figures are only intended to illustrate the method according tothe present invention. Thus, the invention is in no way restricted tothe embodiments described above or defined in the Claims, instead, manydifferent variations and adaptations of the invention, which arepossible within the scope of the inventive idea defined in theaccompanying Claims, will be obvious to one versed in the art.

1. A method in a paper or pulp process to control the chemical state ofthe pulp and circulation water system, in which said process one or moreraw-material components (PROCESS WATER, TMP, PULP, REJECT) diluted inliquid, possible fillers, and one or more additives are mixed to formstock, characterized in that the electrochemical state of at least oneraw-material component (PROCESS WATER, TMP, PULP, REJECT) and/or thestock is regulated to control the reactions between the raw-materialcomponents (PROCESS WATER, TMP, PULP, REJECT), without the regulationsubstantially affecting the pH values of the raw-material components(PROCESS WATER, TMP, PULP, REJECT) and/or of the stock.
 2. A methodaccording to claim 1, characterized in that the electrochemical state ofthe raw-material component (PROCESS WATER, TMP, PULP, REJECT) and/or thestock is regulated by adding a reducing agent, such as sulphur dioxideSO₂, to it.
 3. A method according to claim 1, characterized in that theelectrochemical state of the raw-material component (PROCESS WATER, TMP,PULP, REJECT) and/or the stock is regulated by adding an oxidizing agentsuch as hydrogen peroxide H₂O₂, to it.
 4. A method according to claim 1,characterized in that the electrochemical state of the raw-materialcomponent (PROCESS WATER, TMP, PULP, REJECT) is regulated with the aidof an external current source.
 5. A method according to claim 1,characterized in that the electrochemical state of the raw-materialcomponent (PROCESS WATER, TMP, PULP, REJECT) is regulated with the aidof an external magnetic field.
 6. A method according to claim 1,characterized in that the electrochemical state of the raw-materialcomponent (PROCESS WATER, TMP, PULP, REJECT) is regulated with the aidof a gas.
 7. A method according to claim 1, characterized in that theelectrochemical state of the raw-material component (PROCESS WATER, TMP,PULP, REJECT) is determined by measuring the electrochemical state ofthe dilution liquid in relation to at least one reference electrode. 8.A method according to claim 1 characterized in that the electrochemicalstate of the raw-material component (PROCESS WATER, TMP, PULP, REJECT)is regulated before it is fed into the mixing tank.
 9. A methodaccording to claim 1, characterized in that the regulation of theelectrochemical state is carried out in pulses and/or by changingpolarity.
 10. A method according to claim 1, characterized in that atleast one raw-material component (PROCESS WATER, TMP, PULP, REJECT) isdivided into at least two parts and the electrochemical state of atleast one part is regulated before the parts are combined to achieve thedesired reactions.